Burner with oxygen and fuel mixing apparatus

ABSTRACT

An apparatus is provided for combining oxygen and fuel to produce a mixture to be burned in a burner. The oxygen-fuel mixture is ignited in a fuel-ignition zone in a flame chamber to produce a flame.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/303,198, filed Nov. 23, 2011, the entire specification of which isincorporated herein by reference.

BACKGROUND

The present disclosure relates to burner assemblies, and particularly tooxygen-fuel burner assemblies. More particularly, the present disclosurerelated to apparatus for using recycled flue gas in a burner assembly.

SUMMARY

According to the present disclosure, an apparatus is provided forcombining oxygen and fuel to produce a mixture to be burned in a burner.The apparatus comprises a fuel supply tube configured to communicate astream of fuel to a fuel-ignition zone provided, for example, by a flamechamber formed in a refractory shape coupled to a downstream end of thefuel supply tube. The apparatus further includes an oxygen supply tubefor conducting oxygen to an oxygen-fuel mixer configured to dischargeoxygen into the stream of fuel flowing through the fuel supply tube toproduce an oxygen-fuel mixture that is discharged into the fuel-ignitionzone in the flame chamber.

In illustrative embodiments, an apparatus is provided for combiningrecycled flue gas, oxygen, and fuel to produce an ignitable fluid to beburned in a burner. The apparatus comprises a primary oxygen supply tubeand a fuel supply tube. The fuel supply tube is formed to include a fueltransport passageway and oxygen-injection holes opening into the fueltransport passageway. The fuel supply tube is arranged to extend intothe primary oxygen supply tube to form an oxygen flow passagetherebetween to communicate a primary stream of oxygen flowing in theoxygen flow passage through the oxygen-injection holes formed in thefuel supply tube to mix with fuel conducted through the fuel transportpassageway prior to combustion to produce a combustible oxygen-fuelmixture. The apparatus further includes flue-gas recycling means forcombining a secondary stream of oxygen and a first stream of recycledflue gas to flow in a first recycled flue gas passage that is separatedfrom the oxygen flow passage to produce a first stream ofoxygen-enriched flue gas separately from the combustible oxygen-fuelmixture and for combining the first stream of oxygen-enriched flue gasand the combustible oxygen-fuel mixture to produce an ignitable fluid ina flame chamber arranged to communicate with the fuel transportpassageway and the first recycled flue gas passage. In illustrativeembodiments, the apparatus further includes oxygen-distributioncontroller means for varying the volume percentage of oxygen in each ofthe combustible oxygen-fuel mixture and the first stream ofoxygen-enriched flue gas to provide the ignitable fluid with an oxygencontent of at least 20.9% so that the ignitable fluid can be ignited toproduce a burn for various ranks of fuel and recycled flue gas admittedinto the burner to produce the combustible oxygen-fuel mixture and theoxygen-enriched flue gas.

Various combinations of oxygen-fuel mixtures and recycled flue gascooperate to produce an ignitable fluid that is suitable to be ignitedin a flame chamber of an air-fuel combustion system. In a firstillustrative embodiment, the ignitable fluid comprises an oxygen-fuelmixture and a first stream of oxygen-enriched flue gas. In a secondillustrative embodiment, the ignitable fluid further comprises a secondstream of (non-oxygen-enriched) flue gas. In a third illustrativeembodiment, the ignitable fuel instead further comprises a second streamof oxygen-enriched flue gas.

Additional features of the present disclosure will become apparent tothose skilled in the art upon consideration of illustrative embodimentsexemplifying the best mode of carrying out the disclosure as presentlyperceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a diagrammatic illustration of an oxygen-fuel-flue gascombustion system in accordance with a first embodiment of the presentdisclosure showing that the system includes an illustrative burnerformed to include a fuel inlet provided in a fuel supply tube, a primaryoxygen supply inlet provided in an upstream elbow-shaped firstoxygen-transfer tube associated with a primary oxygen supply tube thatextends along, around, and in concentric relation to the fuel supplytube, a secondary oxygen supply inlet provided in a downstreamelbow-shaped second oxygen transfer tube associated with a secondaryoxygen supply tube, and a recycled flue gas inlet;

FIG. 1A is an enlarged perspective view of the burner of FIG. 1 withdownstream portions broken away to show an annular flow passage formedin a recycled flue gas supply tube that surrounds a downstream end ofthe primary oxygen supply tube and some upstream radial vanes and somedownstream swirl vanes mounted on the primary oxygen supply tube andarranged to lie in that annular flow passage;

FIG. 2 is a front elevation view of the burner of FIGS. 1 and 1A;

FIG. 3 is a bottom view of the burner of FIG. 2;

FIG. 4 is a side elevation view of the burner of FIG. 2;

FIG. 5 is a sectional and diagrammatic view of the oxygen-fuel-flue gascombustion system shown in FIG. 1 showing a burner block formed toinclude a flame chamber containing a flame, a primary oxygen supply tubecontaining a fuel supply tube including an oxygen-fuel mixer formed toinclude means for conducting oxygen extant in an oxygen flow passageprovided in the oxygen supply tube into a stream of fuel passing througha fuel transport passageway provided in the fuel supply tube toward theflame chamber to produce a combustible oxygen-fuel mixture, a recycledflue gas supply tube containing a downstream portion of the primaryoxygen supply tube, and a short secondary oxygen supply tube containinga midstream portion of the primary oxygen supply tube and discharging asecondary stream of oxygen in an axial direction into recycled flue gasflowing in a flue gas passage provided in the recycled flue gas supplytube to produce a stream of oxygen-enriched flue gas that is firstchanneled by upstream radial vanes coupled to the primary oxygen supplytube and second swirled by downstream swirl plates coupled to theprimary oxygen supply tube and provided in the flue gas passage and thencombined in the flame chamber with the combustible oxygen-fuel mixturethat is discharged from the oxygen-fuel nozzle to produce an ignitablefluid;

FIG. 6 is a diagrammatic illustration of an oxygen-fuel-flue gascombustion system in accordance with a second embodiment of the presentdisclosure showing that the system includes an illustrative burnerformed to include a fuel inlet provided in a fuel supply tube, a primaryoxygen supply inlet provided in an elbow-shaped first oxygen-transfertube associated with a primary oxygen supply tube, a secondary oxygensupply inlet provided in a short straight second oxygen-transfer tubecoupled to a circular upstream portion of a secondary oxygen supplytube, a recycled flue gas first stream inlet, and a recycled flue gassecond stream inlet;

FIG. 6A is an enlarged perspective view of the burner of FIG. 6 withdownstream portions broken away to show various flow passages providedin the two recycled flue gas supply tubes and showing various upstreamradial vanes and downstream swirl vanes;

FIG. 7 is a front elevation view of the burner of FIGS. 6 and 6A;

FIG. 8 is a bottom view of the burner of FIG. 7;

FIG. 9 is a side elevation view of the burner of FIG. 7;

FIG. 10 is a sectional and diagrammatic view of the oxygen-fuel-flue gascombustion system shown in FIG. 6 showing a burner block formed toinclude a flame chamber containing a flame, a primary oxygen supply tubecontaining a fuel supply tube including an oxygen-fuel mixer formed toinclude means for conducting oxygen extant in an oxygen flow passageprovided in the oxygen supply tube into a stream of fuel passing througha fuel transport passageway provided in the fuel supply tube toward theflame chamber to produce a combustible oxygen-fuel mixture, a firstrecycled flue gas supply tube containing a downstream portion of theprimary oxygen supply tube, a second recycled flue gas supply tubecontaining a downstream portion of the first recycled flue gas supplytube, and a secondary oxygen supply tube surrounding a midstream portionof the primary oxygen supply tube and discharging a series of radiallydirected secondary streams of oxygen into a first stream of recycledflue gas flowing in a flue gas passage provided in the first recycledflue gas supply tube to produce a stream of oxygen-enriched flue gasthat is first channeled up upstream radial vanes coupled to the primaryoxygen supply tube and second swirled by swirl plates coupled to theprimary oxygen supply tube and provided in the flue gas passage of thefirst recycled fluid gas supply tube and then combined in the flamechamber with the combustible oxygen-fuel mixture to provide anoxygen-enriched fluid and showing that an inert (non-oxygen-enriched)second stream of recycled flue gas is discharged into a flue gas passageprovided in the second flue gas supply tube and conducted into the flamechamber to combine with the oxygen-enriched fluid therein to produce anignitable fluid;

FIG. 11 is a diagrammatic illustration of an oxygen-fuel-flue gascombustion system in accordance with a third embodiment of the presentdisclosure showing that the system includes an illustrative burnerformed to include a fuel inlet provided in a fuel supply tube, a primaryoxygen supply inlet provided in an upright oxygen-transfer tubeassociated with a primary oxygen supply tube that extends along ahorizontal central axis established by the fuel supply tube, a flue-gasdistributor configured to receive recycled flue gas and partitioned toinclude a front gas chamber associated with a pivotable frontflow-control valve and a rear gas chamber associated with a pivotablerear flow-control valve, a secondary oxygen supply inlet provided in asecondary oxygen supply tube located behind a front portion of theflue-gas distribution box and coupled in fluid communication to thefront gas chamber as suggested in FIG. 11A, and a tertiary oxygen supplyinlet provided in a tertiary oxygen supply tube located behind a rearportion of the flue-gas distribution box and coupled in fluidcommunication to the rear gas chamber as suggested in FIG. 11A;

FIG. 11A is a sectional perspective view of the burner of FIG. 11coupled to a downstream burner block that is formed to include adiverging flame chamber;

FIG. 12 is a front elevation view of the burner of FIGS. 11 and 11A;

FIG. 13 is a bottom view of the burner of FIGS. 11 and 11A;

FIG. 14 is a side elevation view of the burner of FIGS. 11 and 11A; and

FIG. 15 is a sectional and diagrammatic view of the oxygen-fuel-glue gascombustion system shown in FIG. 6 showing a burner block formed toinclude a flame chamber containing a flame, a primary oxygen supply tubecontaining a fuel supply tube including an oxygen fuel mixer formed toinclude means for conducting oxygen extant in an oxygen flow passageprovided in the primary oxygen supply tube into a stream of fuel passingthrough a fuel transport passageway provide in the fuel supply tubetoward the flame chamber to produce a combustible oxygen-fuel mixture, afirst recycled flue gas supply tube containing a downstream portion ofthe primary oxygen supply tube and receiving a first stream ofoxygen-enriched flue gas discharged from the front gas chamber formed inthe flue-gas distributor into a first flue gas passage formed in thefirst recycled flue gas supply tube, a second recycled flue gas supplytube containing a downstream portion of the first recycled flue gassupply tube and receiving a second stream of oxygen-enriched flue gasdischarged from the rear gas chamber formed in the flue-gas distributorinto a second flue gas passage formed in the second recycled flue gassupply tube and showing that each of the first and second streams ofoxygen-enriched flue gas is first swirled by swirl plates coupled to theprimary oxygen supply tube and then combined in the flame chamber withthe combustible oxygen-fuel mixture to provide an ignitable fluid in anignition zone in the flame chamber.

DETAILED DESCRIPTION

Oxygen-fuel-flue gas combustion systems are disclosed herein forcombining oxygen, fuel, and recycled flue gas to produce an ignitablefluid in a flame chamber. A combustion system 10 in accordance with afirst embodiment of the present disclosure is illustrated in FIGS. 1-5and includes oxygen-enriched flue gas stream 10B in an ignitable fluid28. A combustion system 100 in accordance with a second embodiment ofthe present disclosure is illustrated in FIGS. 6-10 and includes a firststream 100B of oxygen-enriched flue gas and a second stream 332 of inert(non-oxygen enriched) recycled flue gas in an ignitable fluid 128. Acombustion system 200 in accordance with a third embodiment of thepresent disclosure is illustrated in FIGS. 11-15 and includes first andsecond streams 200B1, 200B2 oxygen-enriched flue gas in an ignitablefluid 228.

A combustion system 10 for burning oxygen, fuel, and recycled flue gasto produce a flame 12 is shown in perspective in FIG. 1 and in sectionin FIG. 5. System 10 comprises a fuel supply tube 14, a primary oxygensupply tube 16, a secondary oxygen supply tube 18, a recycled flue gassupply tube 21, and a burner block 23 formed to include a flame chamber24 as suggested in FIG. 5. An igniter 26 is provided to ignite a fluid28 extant in flame chamber 24 to produce flame 12 as also suggested inFIG. 5. Ignitable fluid 28 (in this first embodiment) comprises: (1)oxygen-fuel mixture 10A and (2) oxygen-enriched flue gas 10B. Ignitablefluid 28 is adapted to be combusted in a flame chamber of an air-fuelcombustion system even though it has been enriched with oxygen inaccordance with the present disclosure.

Fuel supply tube 14 has a horizontal central axis 14A and has a firedopened end 14F communicating with flame chamber 24 as suggested in FIG.5. Fuel supply tube 14 comprises an upstream section 14U providing afuel inlet port 14I, a downstream section 14D including fired opened end14F, and an oxygen-fuel mixer 14M formed to include a series ofoxygen-inlet ports 14P extending about the circumference of fuel supplytube 14 and arranged to interconnect upstream and downstream sections14U, 14D. Upstream section 14U, oxygen-fuel mixer 14M, and downstreamsection 14D cooperate to form a fuel transport passageway 14T extendingalong the length of fuel supply tube 14 from fuel inlet port 14I tofired opened end 14F to conduct fuel 30F from fuel supply 30 to flamechamber 24. In an illustrative embodiment, oxygen-fuel mixer 14M is anozzle configured to decelerate flow of fuel 30F passing therethroughduring injection of primary oxygen 34P through oxygen-inlet ports 14P tomaintain a substantially uniform flow rate in portions of fuel transportpassage 14T included in upstream and downstream sections 14U, 14D.

Primary oxygen supply tube 16 extends around and in concentric relationto fuel supply tube 14 as suggested in FIG. 5 to define an annularoxygen flow passage 16F around and along fuel supply tube 14. Anupstream section of primary oxygen supply tube 16 is coupled to a firstoxygen-transfer tube 32 that is formed to include a primary oxygensupply inlet 321. A primary stream 34P of oxygen is constrained to flowfrom oxygen supply 34, in series, through first oxygen-transfer tube 32,oxygen flow passage 16F, and oxygen-inlet ports 14P formed inoxygen-fuel mixer 14M to mix with fuel 30F flowing through fueltransport passageway 14T to produce a combustible oxygen-fuel mixture10A that is discharged from fired opened end 14F of fuel supply tube 14into a flame-ignition zone 24FIZ provided in flame chamber 24 assuggested in FIG. 5.

Secondary oxygen supply tube 18 extends around and in concentricrelation to a midstream section of primary oxygen supply tube 16 assuggested in FIG. 5 to define an annular plenum 18P and severaloxygen-discharge outlets 18O. Each oxygen-discharge outlet 18O isarranged to open into plenum 18P and to discharge a stream 34S ofsecondary oxygen flowing through plenum 18P into a downstream annularrecycled flue gas passage 21F formed between primary oxygen supply tube16 and the surrounding recycled flue gas supply tube 21 to produce astream of oxygen-enriched flue gas 10B as suggested in FIG. 5. Thisflowing stream of oxygen-enriched flue gas 10B is first channeled byradial vanes 21V provided in recycled flue gas passage 21F and thenswirled by swirl vanes 21S provided in recycled flue gas passage 21F assuggested in FIGS. 1A and 5.

In illustrative embodiments, oxygen-discharge means is coupled tosecondary oxygen supply tube 18 for discharging a stream 34S ofsecondary oxygen flowing through plenum 18P in an axial direction 35A insubstantially spaced-apart parallel relation to central axis 14A to mixwith recycled flue gas 33 flowing through recycled flue gas passage 21Fas suggested in FIG. 5. In an illustrative embodiment, theoxygen-discharge means comprises a discharge tube 18T arranged to lie insubstantially spaced-apart parallel relation to primary oxygen supplytube 16. Discharge tube 18T is formed to include an oxygen inlet portaligned in fluid communication with the oxygen-discharge outlet 18Oformed in secondary oxygen supply tube 18 and an oxygen outlet portarranged to open toward the downstream flame chamber 24 as suggested inFIG. 5. It is within the scope of this disclosure to provide severalcircumferentially spaced-apart discharge tubes 18T on a rearwardlyfacing annular wall 18W included in secondary air supply tube 18 assuggested in FIG. 5.

An upstream section of secondary oxygen supply tube 18 is coupled to asecond oxygen-transfer tube 36 that is formed to include secondaryoxygen supply inlet 36I. A secondary stream 34S of oxygen is constrainedto flow from oxygen supply 34, in series, through second oxygen-transfertube 36, plenum 18P, and discharge tube 18T to mix with recycled fluegas 33 flowing through recycled flue gas passage 21F to produce anoxygen-enriched flue gas 10B that is discharged into the flame-ignitionzone 24F in flame chamber 24 to combine with the oxygen-fuel mixture 10Aextant therein to produce ignitable fluid 28 as suggested in FIG. 5.This ignitable fluid 28 produced in accordance with the presentdisclosure can be combusted in the flame chamber of an air-fuelcombustion system even though it has been enriched with oxygen inaccordance with the present disclosure.

A combustion system 100 for burning oxygen, fuel, and recycled flue gasin accordance with a second embodiment of the disclosure to produce aflame 12 is shown in perspective in FIG. 6 and in section in FIG. 10.System 100 comprises a fuel supply tube 14, a primary oxygen supply tube16, a secondary oxygen supply tube 118, a first recycled flue gas supplytube 21, a second recycled flue gas supply tube 22, and a burner block23 formed to include a flame chamber 24 as suggested in FIG. 5. Anigniter 26 is provided to ignite an ignitable fluid 128 extant in flamechamber 24 to produce flame 12 as also suggested in FIG. 10. Ignitablefluid 128 (in this second embodiment) comprises: (1) oxygen-fuel mixture10A; (2) oxygen-enriched flue gas 100B; and (3) recycled flue gas 332.Ignitable fluid 128 is adapted to be combusted in a flame chamber of anair-fuel combustion system even though it has been enriched with oxygenin accordance with the present disclosure.

Fuel supply tube 14 has a horizontal central axis 14A and has a firedopened end 14F communicating with flame chamber 24 as suggested in FIG.10. Fuel supply tube 14 comprises an upstream section 14U providing afuel inlet port 14I, a downstream section 14D including fired opened end14F, and an oxygen-fuel mixer 14M formed to include a series ofoxygen-inlet ports 14P extending about the circumference of fuel supplytube 14 and arranged to interconnect upstream and downstream sections14U, 14D. Upstream section 14U, oxygen-fuel mixer 14M, and downstreamsection 14D cooperate to form a fuel transport passageway 14T extendingalong the length of fuel supply tube 14 from fuel inlet port 14I tofired opened end 14F to conduct fuel 30F from fuel supply 30 to flamechamber 24. In an illustrative embodiment, oxygen-fuel mixer 14M is anozzle configured to decelerate flow of fuel 30F passing therethroughduring injection of primary oxygen 34P through oxygen-inlet ports 14P tomaintain a substantially uniform flow rate in portions of fuel transportpassage 14T included in upstream and downstream sections 14U, 14D.

Primary oxygen supply tube 16 extends around and in concentric relationto fuel supply tube 14 as suggested in FIG. 10 to define an annularoxygen flow passage 16F around and along fuel supply tube 14. Anupstream section of primary oxygen supply tube 16 is coupled to a firstoxygen-transfer tube 32 that is formed to include a primary oxygensupply inlet 32I. A primary stream 34P of oxygen is constrained to flowfrom oxygen supply 34, in series, through first oxygen-transfer tube 32,oxygen flow passage 16F, and oxygen-inlet ports 14P formed inoxygen-fuel mixer 14M to mix with fuel 30F flowing through fueltransport passageway 14T to produce a combustible oxygen-fuel mixture10A that is discharged from fired opened end 14F of fuel supply tube 14into a flame-ignition zone 24FIZ provided in flame chamber 24 assuggested in FIG. 10.

Secondary oxygen supply tube 118 extends around and in concentricrelation to a midstream section of primary oxygen supply tube 16 assuggested in FIG. 10 to define an annular plenum 118P and severaloxygen-discharge outlets 118O. Each oxygen-discharge outlet 180 isarranged to open into plenum 118P and to discharge a stream 34S ofsecondary oxygen flowing through plenum 118P into a downstream annularrecycled flue gas passage 21F formed between primary oxygen supply tube116 and the surrounding first recycled flue gas supply tube 21 toproduce a first stream 100B of oxygen-enriched flue gas as suggested inFIG. 10. This flowing stream 100B of oxygen-enriched flue gas is firstchanneled by radial vanes 21V provided in recycled flue gas passage 21Fand then swirled by swirl vanes 21S provided in recycled flue gaspassage 21F as suggested in FIGS. 6, 6A, and 10.

In illustrative embodiments, oxygen-discharge means is coupled tosecondary oxygen supply tube 118 for discharging a stream 34S ofsecondary oxygen flowing through plenum 118P in a radial direction 35Rtoward central axis 14A of fuel supply tube 14 to mix with a firststream 331 of recycled flue gas 33 flowing through recycled flue gaspassage 21F as suggested in FIG. 10. In an illustrative embodiment, theoxygen-discharge means comprises a discharge tube 118T arranged to liein substantially spaced-apart parallel relation to primary oxygen supplytube 16. Discharge tube 118T is formed to include an oxygen inlet portaligned in fluid communication with the oxygen-discharge outlet 118Oformed in secondary oxygen supply tube 118 and a series of, for example,five oxygen-discharge ports arranged to open toward an exterior surfaceof primary oxygen supply tube 16 as suggested in FIG. 10. It is withinthe scope of this disclosure to provide several circumferentiallyspaced-apart discharge tubes on a rearwardly facing annular wall 118Wincluded in secondary air supply tube 118 as suggested in FIGS. 6, 6A,and 10.

An upstream section of secondary oxygen supply tube 118 is coupled to asecond oxygen-transfer tube 136 that is formed to include secondaryoxygen supply inlet 136I. A secondary stream 34S of oxygen isconstrained to flow from oxygen supply 34, in series, through secondoxygen-transfer tube 136, plenum 118P, and discharge tube 118T to mixwith a first stream 331 of recycled flue gas 33 flowing through recycledflue gas passage 21F to produce an oxygen-enriched flue gas 100B1 thatis discharged into the flame-ignition zone 24F1Z in flame chamber 24 tocombine with the oxygen-fuel mixture 10A extant therein as suggested inFIG. 10.

First recycled flue gas supply tube 21 is arranged to extend into secondrecycled flue gas supply tube 22 to form a second recycled gas passage22F therebetween as suggested in FIG. 10. A second stream 332 ofrecycled flue gas (that is not enriched with oxygen) is diverted fromthe supply of recycled flue gas 33 and constrained to flow in secondrecycled flue gas passage 22F without exposure to the secondary stream34S of oxygen discharged into first recycled flue gas passage 21F assuggested in FIG. 10. This second stream 332 of recycled flue gascombines as suggested in FIG. 10 with oxygen-fuel mixture 10A and firststream 100B of oxygen-enriched flue gas in flame-ignition zone 24F1Z inflame chamber 24 to produce ignitable fluid 128. This ignitable fluid128 produced in accordance with the present disclosure can be combustedin the flame chamber of an air-fuel combustion system even though it hasbeen enriched with oxygen in accordance with the present disclosure.

A combustion system 200 for burning oxygen, fuel, and recycled flue gasin accordance with a third embodiment of the disclosure to produce aflame 12 is shown in perspective in FIG. 11 and in section in FIG. 15.System 200 comprises a fuel supply tube 14, a primary oxygen supply tube16, a secondary oxygen supply tube 218, a tertiary oxygen supply tube219, a flue-gas distributor 220, a first recycled flue gas supply tube221, a second recycled flue gas supply tube 222, and a burner block 23formed to include a flame chamber 24 as suggested in FIG. 5. An igniter26 is provided to ignite an ignitable fluid 228 extant in flame chamber24 to produce flame 12 as also suggested in FIG. 15. Ignitable fluid 228(in this third embodiment) comprises: (1) oxygen-fuel mixture 10A; (2)first stream 100B1 of oxygen-enriched flue gas; and (3) second stream100B2 of recycled flue gas. Ignitable fluid 228 is adapted to becombusted in a flame chamber of an air-fuel combustion system eventhough it has been enriched with oxygen in accordance with the presentdisclosure.

Fuel supply tube 14 has a horizontal central axis 14A and has a firedopened end 14F communicating with flame chamber 24 as suggested in FIG.15. Fuel supply tube 14 comprises an upstream section 14U providing afuel inlet port 14I, a downstream section 14D including fired opened end14F, and an oxygen-fuel mixer 14M formed to include a series ofoxygen-inlet ports 14P extending about the circumference of fuel supplytube 14 and arranged to interconnect upstream and downstream sections14U, 14D. Upstream section 14U, oxygen-fuel mixer 14M, and downstreamsection 14D cooperate to form a fuel transport passageway 14T extendingalong the length of fuel supply tube 14 from fuel inlet port 14I tofired opened end 14F to conduct fuel 30F from fuel supply 30 to flamechamber 24. In an illustrative embodiment, oxygen-fuel mixer 14M is anozzle configured to decelerate flow of fuel 30F passing therethroughduring injection of primary oxygen 34P through oxygen-inlet ports 14P tomaintain a substantially uniform flow rate in portions of fuel transportpassage 14T included in upstream and downstream sections 14U, 14D.

Primary oxygen supply tube 16 extends around and in concentric relationto fuel supply tube 14 as suggested in FIG. 15 to define an annularoxygen flow passage 16F around and along fuel supply tube 14. Anupstream section of primary oxygen supply tube 16 is coupled to a firstoxygen-transfer tube 132 that is formed to include a primary oxygensupply inlet 132I. A primary stream 34P of oxygen is constrained to flowfrom oxygen supply 34, in series, through first oxygen-transfer tube132, oxygen flow passage 16F, and oxygen-inlet ports 14P formed inoxygen-fuel mixer 14M to mix with fuel 30F flowing through fueltransport passageway 14T to produce a combustible oxygen-fuel mixture10A that is discharged from fired opened end 14F of fuel supply tube 14into a flame-ignition zone 24FIZ provided in flame chamber 24 assuggested in FIG. 15.

Secondary oxygen supply tube 218 is employed to receive a secondarystream 34S of oxygen from oxygen supply 34 as suggested in FIG. 15. Thatsecondary stream 34S of oxygen then leaves secondary oxygen supply tube218 and is later mixed with a first stream 331 of recycled flue gas 33to produce the first stream 200B1 of oxygen-enriched flue gas assuggested in FIG. 15.

Tertiary oxygen supply tube 219 is employed to receive a tertiary stream34T of oxygen from oxygen supply 34 as also suggested in FIG. 15. Thattertiary stream 34T of oxygen then leaves tertiary oxygen supply tube219 and is later mixed with a second stream 332 of recycled flue gas 33to produce the second stream 200B2 of oxygen-enriched flue gas assuggested in FIG. 15.

Each of the first and second streams 200B1, 200B2 of oxygen-enrichedflue gas produced in accordance with this third embodiment of thepresent disclosure can comprise a predetermined oxygen content selectedby a combustion system operator so that the oxygen content of firststream 200B1 of recycled flue gas is different than the oxygen contentof second stream 200B2 of recycled flue gas. This feature enhances theability of an operator of combustion system to manage oxygen contents ofthe various streams of products that are discharged into flame-ignitionzone 24F1Z to establish a desired ratio of oxygen, fuel, and flue gas inan ignitable fluid 228 produced by combination of oxygen-fuel mixture10A and two streams 200B1, 200B2 of oxygen-enriched flue gas. Swirlvanes 221S can be provided as suggested in FIG. 15 to swirl the combinedfirst and second streams 200B1, 200B2 as they are discharged into flamechamber 24.

Flue-gas distributor 220 is configured to provide means for combining astream of secondary oxygen 34S and first stream 331 of recycled flue gasto produce first stream 200B1 of oxygen-enriched flue gas and forcombining a stream of tertiary oxygen 34T and second stream 332 ofrecycled flue gas to produce second stream 200B2 of oxygen-enriched fluegas. Flue-gas distributor 22 includes a housing 220H that is partitionedto form a front gas chamber 22DF associated with secondary oxygen 34Sand a rear gas chamber 220R associated with tertiary oxygen 34T assuggested in FIG. 15.

Front gas chamber 220F of flue-gas distributor 220 has an inlet 220FIfor receiving a first stream 331 of recycled flue gas 33 and an outlet220O in fluid communication with a first flue gas passage 221F formedbetween primary oxygen supply tube 16 and the surrounding first recycledflue gas supply tube 221 as suggested in FIG. 15. Front controller means331C is included in flue-gas distributor 220 for regulating flow offirst stream 331 of recycled flue gas 33 into front gas chamber 220F tomix with secondary oxygen 34S present therein to produce first stream200B1 oxygen-enriched flue gas. In an illustrative embodiment, frontcontroller means 331C comprises a pivotable front flow-control valvemounted for pivotable movement about a pivot axis 331A at the option ofa combustion system operator.

Rear gas chamber 220R of flue-gas distributor 220 has an inlet 220RI forreceiving a second stream 332 of recycled flue gas 33 and an outlet220RO in fluid communication with a second flue gas passage 222F formedbetween first recycled flue gas supply tube 221 and the surroundingsecond recycled flue gas supply tube 222 as suggested in FIG. 15. Rearcontroller means 332 C is included in flue-gas distributor 220 forregulating flow of second stream 332 of recycled flue gas 33 into reargas chamber 220R to mix with tertiary oxygen 34T present therein toproduce second stream 200B2 of oxygen-enriched flue gas. In anillustrative embodiment, rear controller means 332C comprises apivotable rear flow-control valve mounted for pivotable movement about apivot axis 332A at the option of a combustion system operator.

In illustrative embodiments, front oxygen-discharge means is coupled tosecondary oxygen supply tube 218 for discharging a stream 34S ofsecondary oxygen into front gas chamber 220F to mix with a first stream331 of recycled flue gas flowing therethrough to produce a first stream200B1 of oxygen-enriched flue gas as suggested in FIG. 15. In anillustrative embodiment, the front oxygen-discharge means comprises adischarge tube 218T arranged to extend into front gas chamber 220F andto lie in a position between front flow-control valve 331C and primaryoxygen supply tube 16. Discharge tube 218T is formed to include anoxygen inlet port aligned in fluid communication with anoxygen-discharge outlet formed in secondary oxygen supply tube 218 and aseries of, for example, several oxygen-discharge ports arranged to opentoward a front wall of housing 220H. A secondary stream 34S of oxygen isconstrained to flow from oxygen supply 34, in series, through secondaryoxygen supply tube 218 and discharge tube 218T to mix with a firststream 331 of recycled flue gas 33 to produce a first stream 200B2 ofoxygen-enriched flue gas that flows through first recycled flue gaspassage 221F and is discharged into the flame-ignition zone 24F1Z inflame chamber 24 to combine with the oxygen-fuel mixture 10A extanttherein as suggested in FIG. 15.

In illustrative embodiments, rear oxygen-discharge means is coupled totertiary oxygen supply tube 219 for discharging a stream 34T ofsecondary oxygen into rear gas chamber 220R to mix with a second stream332 of recycled flue gas flowing therethrough to produce a second stream200B2 of oxygen-enriched flue gas as suggested in FIG. 15. Inillustrative embodiments, the rear oxygen-discharge means comprises adischarge tube 219T arranged to extend into rear gas chamber 220R and tolie in a position between rear flow-control valve 332C and primaryoxygen supply tube 16. Discharge tube 219T is formed to include anoxygen inlet port aligned in fluid communication with anoxygen-discharge outlet formed in tertiary oxygen supply tube 219 and aseries of, for example, several oxygen-discharge ports arranged to opentoward a front wall of housing 220H as suggested in FIG. 15. A tertiarystream 34T of oxygen is constrained to flow from oxygen supply 34, inseries, through tertiary oxygen supply tube 219 and discharge tube 219Tto mix with second stream 332 of recycled flue gas 33 to produce asecond stream 220B2 of oxygen-enriched flue gas that flows throughsecond recycled flue gas passage 222F and is discharged into theflame-ignition zone 24F1Z in flame chamber 24 to combine withoxygen-fuel mixture 10A and first stream 200B1 of inert flue gas extanttherein as suggested in FIG. 15.

Many existing industrial burner applications such as steam boilers andfired heaters were originally designed to operate using air/fuelcombustion and thus produce large volumes of combustions products. Thesecombustion products are also known as flue gases or furnace gases.

Oxygen-fuel combustion is a facilitating technology in an overall planto reduce greenhouse gases produced from the burning of fossil fuels(carbon capture). Using only oxygen instead of atmospheric air forcombustion significantly reduces the volume of combustion products(e.g., flue gases) at an equivalent fuel input. As a result, to adaptoxygen/fuel technology for many existing industrial air-fuel burnerapplications is ineffective unless substantial costs are borne toredesign and modify heat transfer surfaces and combustion spaces inthese air-fuel burner applications in order to operate an oxygen-fuelcombustion system. Thus, if a boiler or heater owner wanted to replaceair-fuel burners with oxygen-fuel burners, it would require significantexpense to modify those boilers and heaters on site.

In accordance with the present disclosure, flue gas generated by aburner in, for example, a boiler or heater, is recycled and combinedwith oxygen and with an oxygen-fuel mixture to produce an ignitablefluid that has an oxygen content that simulates an air-fuel mixture.This avoids the expense that would otherwise be incurred to reengineerthe boilers and heaters to accept oxygen-fuel burners and yet maintainsthe air-fuel combustion design performance associated with thoseexisting air-fuel boilers and heaters.

Flue gas itself is not a fluid that would normally be discharged into anignition-zone in a flame chamber of a combustion system. Flue gasgenerated by oxygen-fuel combustion, conditioned and cleaned inpreparation for recycle use, contains, for example, over 90% carbondioxide (CO₂). Carbon dioxide is an inert gas and is used commonly infire extinguishers and not in flame chambers. Under recycle conditions,the presence of flue gas in an ignition zone in a flame chamber would beexpected to create flame instability, poor combustion performance, andunacceptable percentages of unburned fuel or even complete extinction ofany flame in the flame chamber. A burner in accordance with the presentdisclosure is designed to enrich recycled flue gas with oxygen to createan oxygen-enriched flue gas that can be combined with an oxygen-fuelmixture in a flame chamber to produce an ignitable fluid whilemaintaining flame stability and producing industry-accepted combustionperformance and emissions that are required to advance carbon capturetechnology for fossil fuel fired applications.

In accordance with the present disclosure, inert recycled flue gas isused to transport fuel passing through the fuel transport passagewayformed in the fuel supply tube.

In accordance with the present disclosure, an oxygen-fuel mixer includedin the fuel supply tube and arranged to receive oxygen from a primaryoxygen supply tube provides increased flame stability by injectingoxygen from the primary oxygen supply tube into the inert flue gas andfuel mixture flowing through the fuel supply tube just upstream of thefuel-ignition zone in the flame chamber and the ignition point of thefuel. A suitable fuel may be used such as, for example, fluidizedpulverized solid fuel. This injected oxygen from the primary oxygensupply tube enriches the fuel in the fuel supply tube to produce anoxygen-fuel mixture characterized by an oxygen level favorable for fuelignition and flame stability.

In accordance with the present disclosure, recycled flue gas istransported to the burner through the existing combustion air windboxprovided with existing air fuel burners. The recycled flue gas entersthe burner in accordance with the present disclosure and passes throughan oxygen distribution and injection means for enriching the recycledflue gas with oxygen from a secondary oxygen supply tube to create anoxygen-enriched flue gas. This oxygen-enriched flue gas is thendischarged into the flame chamber and combined with the oxygen-fuelmixture therein to produce an ignitable fluid that allows for the burnerto complete the burn that is begun at the exit of the fuel supply tubedownstream from the oxygen-fuel mixer.

Varying the volume percentage of oxygen in the oxygen-fuel mixturedischarged from the fuel supply tube and in the oxygen-enriched flue gasallows for adjustment of the burn for various ranks of fuels and alsohas the added benefit of providing reductions in produced oxides ofnitrogen pollution common to the burning of fossil fuels. Reductions inproduced carbon monoxide and LOI (a measure of how completely a solidfuel is consumed) are also possible through adjustment of the oxygencontent in the oxygen-fuel mixture and the oxygen-enriched flue gas inaccordance with the present disclosure.

A burner in accordance with the present disclosure can be fabricatedfrom steel and alloy components. A fuel supply tube is provided in thecenter of the burner to transport any suitable fuel. It is within thescope of this disclosure to use some of the recycled flue gas tofluidize and transport pulverized solid fuel in the fuel transportpassageway 14T formed in the fuel supply tube 14. A primary oxygensupply tube 16 receives the fuel supply tube therein and is sealed at afired end downstream of an oxygen-fuel mixer 14M formed in the fuelsupply tube 14 to create a primary oxygen flow passage 16F forconducting a stream of primary oxygen 34P to the oxygen-fuel mixer 14M.This stream of primary oxygen 34P enters the fuel transport passageway14T and mixes with fuel 30F flowing therethrough at a point justupstream from the point of ignition in the flame chamber 24.

In accordance with the present disclosure, recycled flue gas iscollected and passed by a mixing an distribution means (in a flue gaspassage separate from the fuel supply tube and primary oxygen supplytube) to inject oxygen into the recycled flue gas to produceoxygen-enriched flue gas. This oxygen-enriched flue gas then passesforward and around the oxygen-fuel mixer through an annular area definedbetween an exterior surface of the primary oxygen supply tube and aninterior surface of the recycled flue gas supply tube. Theoxygen-enriched flue gas then passes through an adjustable swirlerconfigured to create a swirling flow at the point in the flame chamber24 where the oxygen-fuel mixture and the oxygen-enriched flue gas exitsthe burner. This swirling flow helps to combine those mixtures andassists in stabilizing a flame produced in the flame chamber 24. Theoxygen-enriched flue gas introduces into the flame chamber 24 thebalance of the oxygen flow required to complete combustion of the fuel.

A third annular area is created between the exterior surface of thefirst recycled flue gas supply tube and the interior surface of asurrounding second recycled flue gas supply tube in certain embodimentsin accordance with the present disclosure when it is desired to have anoxygen content of greater than or equal to 20.9% in ignitable fluidproduced by combining the oxygen-fuel mixture and the oxygen-enrichedflue gas. The intent in accordance with the present disclosure is topass the required flue gas volume to simulate air-fuel furnaceconditions, while at the same time creating oxygen-rich primary andsecondary zones in the flame chamber 24 which can be adjusted inaccordance with the present disclosure to create optional flame andemissions performance. The ability in accordance with the presentdisclosure to create oxygen concentrations greater than or equal to20.9% in the primary and secondary flame zones in the flame chamber 24allows the use of previously unacceptable low-rank coals and low BTUcontent fuel gases to be used as fuel while producing acceptableemissions and thermal performance.

The invention claimed is:
 1. A method for combining recycled flue gas,oxygen, and fuel to produce an ignitable fluid, comprising: mixing aprimary stream of oxygen from a primary oxygen supply tube of acombustion system with pulverized fuel and a transport gas from a fuelsupply tube of the combustion system to produce a combustibleoxygen-fuel mixture; combining a secondary stream of oxygen and a streamof recycled flue gas to produce a stream of oxygen-enriched flue gasthat is separate from the combustible oxygen-fuel mixture, whereincombining the secondary stream of oxygen and the stream of recycled fluegas includes: receiving, by a plenum formed between the primary oxygensupply tube and a secondary oxygen supply tube arranged to surround theprimary oxygen supply tube, the secondary stream of oxygen; anddischarging, from the plenum in a radial direction toward a central axisextending through the fuel supply tube, the secondary stream of oxygento combine with the stream of recycled flue gas in the recycled flue gaspassage, wherein the secondary oxygen supply tube includes an annulardownstream portion separated from the primary oxygen supply tube andformed to include the plenum and the oxygen discharge outlet and atubular upstream portion coupled to the annular downstream portion andarranged to lie in spaced-apart side-by-side relation to the primaryoxygen supply tube; and combining the stream of oxygen-enriched flue gasand the combustible oxygen-fuel mixture to produce an ignitable fluid.2. The method of claim 1, wherein the combustible oxygen-fuel mixturehas an oxygen content in excess of 20.9%.
 3. The method of claim 1,wherein the stream of oxygen-enriched flue gas has an oxygen content inexcess of 20.9%.
 4. The method of claim 1, wherein the ignitable fluidhas an oxygen content of at least 20.9%.
 5. The method of claim 1,wherein the stream of recycled flue gas includes non-oxygen-enrichedinert recycled flue gas.
 6. The method of claim 1, wherein the methodincludes combining the stream of oxygen-enriched flue gas, thecombustible oxygen-fuel mixture, and an additional stream of recycledflue gas to produce the ignitable fluid.
 7. A method for combiningrecycled flue gas, oxygen, and fuel to produce an ignitable fluid,comprising: mixing a primary stream of oxygen from a primary oxygensupply tube of a combustion system with fuel and a transport gas from afuel supply tube of the combustion system to produce a combustibleoxygen-fuel mixture; combining a secondary stream of oxygen and a streamof recycled flue gas to produce a stream of oxygen-enriched flue gasthat is separate from the combustible oxygen-fuel mixture, whereincombining the secondary stream of oxygen and the stream of recycled fluegas includes: receiving, by a plenum formed between a secondary oxygensupply tube of the combustion system and the primary oxygen supply tube,the secondary stream of oxygen; and discharging, from the plenum throughan oxygen-discharge outlet arranged to open into the plenum, thesecondary stream of oxygen into a recycled flue gas passage of thecombustion system to combine with the stream of recycled flue gas in therecycled flue gas passage, wherein the secondary oxygen supply tubeincludes an annular downstream portion separated from the primary oxygensupply tube and formed to include the plenum and the oxygen dischargeoutlet and a tubular upstream portion coupled to the annular downstreamportion and arranged to lie in spaced-apart side-by-side relation to theprimary oxygen supply tube; and combining the stream of oxygen-enrichedflue gas and the combustible oxygen-fuel mixture to produce an ignitablefluid.
 8. The method of claim 7, wherein the fuel from the fuel supplytube is pulverized solid fuel.
 9. The method of claim 7, wherein thetransport gas from the fuel supply tube is atmospheric air.
 10. Themethod of claim 7, wherein the transport gas from the fuel supply tubeis recycled flue gas.
 11. The method of claim 7, wherein discharging thesecondary stream of oxygen into the recycled flue gas passage includesdischarging the secondary stream of oxygen in an axial direction alongan axis parallel to a central axis extending into the recycled flue gaspassage.
 12. The method of claim 7, wherein discharging the secondarystream of oxygen into the recycled flue gas passage includes dischargingthe secondary stream of oxygen in a radial direction toward a centralaxis extending through the fuel supply tube.
 13. The method of claim 7,wherein the fuel and the transport gas from the fuel supply tube mixwith the primary stream of oxygen prior to combustion.
 14. A method forcombining recycled flue gas, oxygen, and fuel to produce an ignitablefluid, comprising: mixing a primary stream of oxygen from a primaryoxygen supply tube of a combustion system with pulverized fuel and atransport gas from a fuel supply tube of the combustion system toproduce a combustible oxygen-fuel mixture having an oxygen concentrationthat is different than 20.9%; combining the secondary stream of oxygenand a stream of recycled flue gas to produce a stream of oxygen-enrichedflue gas that is separate from the combustible oxygen-fuel mixture andhas an oxygen concentration that is different than 20.9%, whereincombining the secondary stream of oxygen and the stream of recycled fluegas includes: receiving, by a plenum formed between the primary oxygensupply tube and a second oxygen supply tube arranged to surround theprimary oxygen supply tube, a secondary stream of oxygen; anddischarging, from the plenum through an oxygen-discharge outlet arrangedto open into the plenum, the secondary stream of oxygen into a recycledflue gas passage of the combustion system to combine with the stream ofrecycled flue gas in the recycled flue gas passage; wherein thesecondary oxygen supply tube includes an annular downstream portionseparated from the primary oxygen supply tube and formed to include theplenum and the oxygen discharge outlet and a tubular upstream portioncoupled to the annular downstream portion and arranged to lie inspaced-apart side-by-side relation to the primary oxygen supply tube;and combining the stream of oxygen-enriched flue gas and the combustibleoxygen-fuel mixture to produce an ignitable fluid having an oxygenconcentration of at least 20.9%.
 15. The method of claim 14, whereinmixing the primary stream of oxygen with the pulverized fuel and thetransport gas includes communicating the primary stream of oxygenthrough oxygen-injection holes formed in the fuel supply tube.
 16. Themethod of claim 14, wherein the ignitable fluid is produced in a flamechamber arranged to communicate with a fuel transport passageway of thefuel supply tube and a recycled flue gas passage.
 17. The method ofclaim 14, wherein combining the secondary stream of oxygen and thestream of recycled flue gas includes constraining the secondary streamof oxygen to flow into a recycled flue gas passage through which thestream of recycled flue gas is flowing.
 18. The method of claim 14,wherein the method includes: combining a stream of tertiary oxygen andan additional stream of recycled flue gas to produce an additionalstream of oxygen-enriched flue gas; and combining the additional streamof oxygen-enriched flue gas, the stream of oxygen-enriched flue gas, andthe combustible oxygen-fuel mixture to produce the ignitable fluid. 19.The method of claim 18, wherein combining the stream of tertiary oxygenand the additional stream of recycled flue gas includes regulating flowof the additional stream of recycled flue gas into a gas chamber havingthe tertiary oxygen present therein.
 20. The method of claim 14, whereincombining the secondary stream of oxygen and the stream of recycled fluegas includes regulating flow of the stream of recycled flue gas into agas chamber having the secondary steam of oxygen present therein.